Age related changes in bone mass have been demonstrated in both men and women. Age and sex related differences hormones, nutritional and physiological variables involved in bone turnover are important in elucidating changes in bone physiology in normal aging and disease. Specifically, the relationship age and sex to changes in body composition, both as a marker of obesity and as a measure of the weight bearing load on bone are important factors in bone status and rates of change. The most dramatic rates of change in bone mass occur at the menopause, and changes of body composition, bone mass, and bone markers and hormones are being investigated in a cohort of peri-menopausal women recruited to the Baltimore Longitudinal Study of Aging, who will be followed at 3 month intervals as they traverse the menopause. These studies will allow for the interpretation of the changes that occur prior to and immediately around the time of the cessation of menses, changes that can only be appreciated in a prospective longitudinal study.